In a cement concrete work mixed in proportion 1: 2: 4 (cement: fine aggregate: coarse aggregate) by volume, the fine aggregate is observed to have a bulking of 10%. If the correction for bulking is NOT applied, what will be the actual dry fine aggregate in the concrete mix proportion?
The 1:2:4 concrete means that it is prepared by mixing 1 part cement, 2 parts fine aggregates, and 4 parts coarse aggregates. The volume of water is about 50-60% of the volume of cement.
In case bucking is not considered the actual dry fine aggregate = 2/1.1 per volume of cement
Bulking:- The increase in the volume of a given mass of fine aggregate caused by the presence of water is known as bulking. Fine aggregate bulk is more than coarse aggregate.
If the bulking of sand is 10% and if the mix ratio is 1: 2: 4, the actual volume of sand used will be 1.1 × 2 =2.2 instead of 2 per unit volume of cement.
If this correction is not applied, the actual dry sand in the concrete will be 1 × 2/1.1 = 1.82, instead of 2 per unit volume of cement. The mix proportion would be 1: 1.82: 4 rather than 1: 2: 4; which indicates lesser concrete production.